A bad decision. This is definitely not the most useful move available.
11. a2a3 White plays a useful move. 11... a7a5 Gukesh decides to prevent b2-b4. A logical decision, but this creates some weaknesses on the queenside. 12. h2h3  12... c8e6  13. g1h2 A good prophylactic move, reminiscent of Anatoly Karpov. White reinforces the pawn on h3 before it's even attacked.